How Fixed Mobile Convergence Works

Based on the old telephone models, cell phones were designed to transmit voices. The first generation of cell phones were basically radios, transmitting an analogue signal through the air to a cell tower. With the second generation of cell phones, voices were digitized, but still sent the same way, via a circuit-switched network that established a connection between two phones, keeping it open for as long as your conversation lasted.

The most popular standard for the second generation cell phones is GSM, or Global System for Mobile Communications, which was developed in Europe, and it is based on a model called Time Division Multiple Access (TDMA) but it isn't the only one [source: GSM Association]. The CDMA (Code Division Multiple Access) system was developed in the United States by Qualcomm [source: CDMA Development Group]. The two systems differ in how they allow multiple users to transmit information over the same airwaves. Each standard has its adherents. T-Mobile, for instance, uses the GSM standard, while AT&T uses CDMA -- and each standard has its own governing body. You can still call a GSM phone from a CDMA phone, and vice versa, but you can't use one type of phone to connect to the other type of network, so a GSM phone needs GSM coverage to get a signal.

The allure of being able to connect to the Internet wherever you are has led to an increase in data plans offered by cell phone companies, bringing us into the third generation of cell phones (AT&T actually calls its network 3G, but there are others, such as the EDGE network offered by T-Mobile, among others). Third generation networks allow larger chunks of data than just voice, but they still transmit data through the cellular phone system, with the same limitations as second generation phones. As different companies with different network standards head toward uniting the fixed and mobile networks, they've taken a number of different paths, and we'll take a look at some of those next.

Frequencies and the FCC

Wireless networks are transmitted via radio waves, just like AM/FM or television signals. As more people get cell phones and more information is transmitted to them, someone has to step in to keep all that traffic from getting gridlocked. In the U.S., the Federal Communications Commission (FCC) serves as traffic cop for the wireless world, from television signals to cell phones to air traffic control.

The frequencies used by cell phone and wireless networks fall in the Ultra High Frequency band between 300 and 3,000 MHz, with different services using chunks of that spectrum. In 2008, the FCC auctioned off the 700MHz spectrum -- AT&T and Verizon purchased licenses to use for 3G and 4G cell phone services. In October 2009, FCC chair Julius Genachowski announced a "Mobile Broadband Agenda," with the goal of expanded high-speed Internet access, and in February 2010, said that the FCC was looking at reallocating portions of the broadcast spectrum to encourage mobile broadband providers.